My friend the "content locust" :(

[Gamemako]

Most people don't know the difference between Vertical and Horizontal progression
- Vertical progression is based on gear level and player level.
- Horizontal progression is based on adding abilities, attributes and skill points to augment your abilities and character stats.

Specifically, you do not seem to understand the difference. Horizonal progression is not about adding abilities and skill points; that is vertical progression as well. Any absolute gain in power is vertical -- you are going up in power for every possible scenario. Going from ilvl70 fending to ilvl70 pentamelded accessories is vertical progression -- though the item level is the same, there's no reason to consider the Fending accessories for any scenario (ever). Horizontal progression is moving into situationally-useful or playstyle-specific equipment which is not necessarily better in every case than the alternative. The focus is generally on incomparables -- things which simply excel at different tasks. In a shooter like Mass Effect 3, this would be like a shotgun and a sniper rifle. Both do a lot of damage with a slow fire rate, but one is highly accurate at range but limited at close range while the other is a shield-breaking death machine up close and nigh-useless at long range. The two are not directly comparable because each offers an advantage in a situation where the other is limited.